The present invention relates generally to electron sources. More specifically, the present invention relates to semiconductor-based electron sources.
Semiconductor-based electron sources that generate focused electron beams may be used for information storage devices, lithographic applications, and other devices using such focused electron beams. Consider the example of storage devices. For decades researchers have been working to increase storage density and reduce storage cost of information storage devices such as magnetic hard-drives, optical drives, and semiconductor random access memory. However, increasing the storage density is becoming increasingly difficult because conventional technologies appear to be approaching fundamental limits on storage density. For instance, information storage based on conventional magnetic recording is rapidly approaching fundamental physical limits such as the superparamagnetic limit, below which magnetic bits are not stable at room temperature.
Storage devices that do not face these fundamental limits are being researched. An example of such an information storage device is described in U.S. Pat. No. 5,557,596. The device includes multiple electron sources having electron emission surfaces that are proximate a storage medium. During write operations, the electron sources bombard the storage medium with relatively high intensity electron beams. During read operations, the electron sources bombard the storage medium with relatively low intensity electron beams.
Size of storage bits in such devices may be reduced by decreasing the electron beam diameter. Reducing the storage bit size increases storage density and capacity and decreases storage cost.
One type of electron source typically used in displays includes a multitude of xe2x80x9cSpindtxe2x80x9d emitters. A Spindt emitter could be used for generating focused electron beams for data storage devices, lithographic applications, and other applications using such focused electron beams. A Spindt emitter has a cone shape and emits an electron beam at the tip of its cone. The cone tip is made as sharp as possible to reduce operating voltage and achieve a small electron beam diameter.
However, there are problems associated with Spindt emitters. Fabrication of sharp emitter tips is difficult and expensive. Focusing the electron beam from a Spindt tip in a temporally and spatially stable manner is difficult. The electron optics that provide the focusing can become complicated. Moreover, Spindt emitters do not operate well in poor vacuums. These problems become especially prominent as the electron beam diameter is reduced below 100 nanometers.
It would be desirable to reduce fabrication cost and improve stability and operability of the electron source, whether a single emitter or a multitude of emitters. It would also be desirable to decrease the electron beam diameter.
According to one aspect of the present invention, an electron source includes a planar emission region; and a focusing structure for the emission region. Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the present invention.